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N.V.S. SHANKAR* et al. ISSN: 2250–3676
[IJESAT] INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE & ADVANCED TECHNOLOGY Volume-2, Issue-2, 233 – 240
IJESAT | Mar-Apr 2012
Available online @ http://www.ijesat.org 233
FLOW SIMULATION TO STUDY THE EFFECT OF FLOW TYPE ON THE
PERFORMANCE OF MULTI – MATERIAL PLATE FIN HEAT SINKS
N.V.S. Shankar1, Rahul Desala
2, VeerlaSrinivas Babu
3, P. Vamsi Krishna
4, M. M. Rao
5
1Asst. Professor, Dept. of Mechanical Engg., SCET, AP, India, [email protected]
2Graduate Student, Dept. of Mechanical Engg., SCET, AP, India, [email protected]
3Graduate Student, Dept. of Mechanical Engg., SCET, AP, India, [email protected] 4Associate Professor, Dept. of IPE, GITAM University, AP, India, [email protected]
5Principal, SCET, AP, India, [email protected]
Abstract
Heat Sinks, in Electronic systems, are devices that cool the hotter body by dissipating the heat to a fluid medium, generally air. These
are used to cool devices such as high-power semiconductor devices, and optoelectronic devices such as high power lasers and light
emitting diodes (LEDs). These are primarily heat exchangers that are used to exchange the heat from the component to the
surroundings so as to avoid the problem of overheating. There are different types of heat sinks 1.Extruded heat sinks 2.Flooded-fin
heat sinks 3. Integrated vapour chamber heat sinks. The most effective heat sink is the one which can dissipate a large amount of heat.
In this paper, numerical simulation using CFD techniques is carried out for different types of heat sinks. Multi-material heat sink in a
computer cabinet is considered so as to study their performance under different flow conditions. Assembly model of cabinet is initially
generated. Motherboard, Rams, Chipset, Chipset heat sink, Processor heat sink and the rest of the components are modelled and then
assembled to the cabinet. A total of 180W maximum heat dissipation was given as input for analysis. The total heat consisted of heat
profile of the processor, 20W heat dissipation each for Ram and chipset. 80mm axial flow fans with 80cfm were used for inlet and
outlet air exits. 40 mm fan was modeled on the chipset and 80mm fan on the processor. Full case flow simulation was carried out and
the results were presented.
Index Terms: Heat Sink, Flow Simulation, Full Case Flow Simulation, CFD.
--------------------------------------------------------------------- *** ------------------------------------------------------------------------
1. INTRODUCTION
The advancements in computing technology led to higher data
processing rates at tremendous speeds and smaller form factor.
This is leading to higher processor temperatures and thus
higher heat dissipation requirement. Higher processor
temperatures lead to malfunctioning of CPU. Thus the major
problem in electronic systems may be defined as increasing
the performance of the processor while keeping the
temperature to a minimum extent. Thus better ways for heat
dissipation are required. Many cooling solutions [1] like using
heat pipes, water cooling and even cooling by using liquid
nitrogen have been developed.
The main criteria to be considered when designing an air
cooled heat sink is the effective utilization of the fin surface
for transfer of heat from a relatively small heat source like
CPU (with large heat generation rate) with high heat flux. The
technological advancements have led to increase in heat loads.
Thus better heat conductors such as copper plates, carbon –
carbon composites [1], doped Aluminum [10, 11] are used to
improve heat spreading from the heat source into heat sinks.
The type of heat sink and air flow in the heat sink also affect
the amount of heat dissipation. Material used for the heat sink
is another important factor that influences the efficiency of the
heat sink.
A desktop computer CPU is a complex system involving a lot
of heat transfer. Processor, Chipset and Rams are considered
as major heat sources. Experimental testing for study of heat
dissipation in a computer cabinet is a costly affair. Thus
prediction of flow pattern is of great interest as it helps in
studying the heat dissipation process. While designing a
desktop, full case flow simulation is very much necessary to
understand the flow pattern and heat transfer happening in the
N.V.S. SHANKAR* et al. ISSN: 2250–3676
[IJESAT] INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE & ADVANCED TECHNOLOGY Volume-2, Issue-2, 233 – 240
IJESAT | Mar-Apr 2012
Available online @ http://www.ijesat.org 234
system. This data can be used for optimizing the design for
better heat transfer.
R. Mohan,et al [1] discussed the process of optimizing the pin
fin and slot parallel plate fin heat sink for thermal
performance. Thermal performance when using copper and
carbon-carbon composite material for heat base were
presented in their work. Dong-Kwon, et al [2] experimentally
compared the performance of plate-fin and pin-fin heat sinks
subjected to impinging flow. Jei Wei [3] gave an overview of
the thermal design and cooling technology development of
Fujitsu’s high performance servers. Thermal management is
outlined in terms of server cabinet, system board and CPU
package. The challenges before cooling solutions were also
discussed. Chyi-Tsong Chen, et al [4] demonstrated how FEM
and GA can be together applied to optimize the shape of heat
sink for better heat dissipation. Takeshi hirasawa, et al [5]
addressed the problems in manufacturing heat sinks that rise
due to size, shape and materials being used.
Flat micro heat pipes are now being used in lot of applications
like personal computers. Yuichi Kimura, et al [6] presented
the results of steady state analysis on flat micro heat pipe. The
steady-state heat transfer characteristics of this heat pipe have
been experimentally confirmed in detail, and a prediction
method for its maximum heat transfer rate is proposed.
Sukhvinder Kang, et al [7] presented a physics based
analytical model to predict the thermal behavior of pin fin heat
sinks in transverse forced flow. Giovanni Cortella[8] showed
how CFD can be used in refrigerator systems design. Ram
Viswanath, et al [9] addressed the multidimensional problem
in which materials and process improvements in packaging
and heat-sink technology are required to minimize thermal
resistance while maintaining an optimal cost for the thermal
solution. Keller and Kurtis [10, 11] discussed the advantages
of using cast heat sinks of aluminum doped with zinc. Tom
Kowalski, et al [12] discussed the use of FNM and CFD to
design the complex electronic cabinet used for high speed
internet connection. M. Davis, et al [13] discussed the use of
thermoelectric materials in cooling solutions for heat sources
of small form factors.
In the present work, performance comparison of multi-
material plate fin heat sink with copper base and aluminum
plate fins, located in a desktop computer as shown in fig 1,
during flooded and impinging flow is presented. A total of
180W heat dissipation is planned. The heat profile of
processor [15, 16], 20W heat dissipation from Ram and
Chipset [1] were given as input. A full case flow simulation is
carried out and the results are compared. Processor
temperature is the important factor considered in present work.
Figure 1: Modeled cabinet with processor, heat sink and
Ram (one side cover plate was made transparent for
showing inner parts)
2. HEAT SINK TYPES Different types of heat sinks have been designed as cooling
solution for heat dissipation problem. These heat sinks are
classified based on various criteria. The classification of heat
sinks is presented in fig 2.
Figure 2: Heat sink classification
When air is forced to flow over the fins by use of a special fan
on the heat sink, then it is called as active heat sink. Figure 3
shows an active heat sink. When no extra fan is used for
circulating air over the fins and the air circulation is purely
due to the case fan, the heat sink is referred as passive. Figure
Heat Sink
Extruded
Flooded
Integrated
Vapour
Chamber
Active
Passive
N.V.S. SHANKAR* et al. ISSN: 2250–3676
[IJESAT] INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE & ADVANCED TECHNOLOGY Volume-2, Issue-2, 233 – 240
IJESAT | Mar-Apr 2012
Available online @ http://www.ijesat.org 235
4 shows a passive heat sink. Passive heat sinks are generally
seen on north bridge chipset in common home desktops.
Figure 5 shows an integrated vapor chamber heat sink.
Figure 3: Active and flooded heat sink
Figure 4: Passive heat sink on a mother board
Figure 5: Integrated Vapour Chamber heat sink
In addition to the above classification, heat sinks are further
classified as extruded, flooded and Integrated Vapor Chamber
heat sinks.
Extruded heat sinks are generally made by extruding
Aluminum or other material. This Heat sink is a single piece.
The fins are rarely rectangular. Figure 6 shows an Extruded
Heat sink. When higher power dissipation is the requirement,
then flooded heat sinks are used. In Flooded heat sinks, the
ratio of the fin thickness to fin pitch can be as low as 1:3[9].
Figure 3 shows a flooded heat sink. It can be observed that the
fins are very close to each other. Integrated vapor chamber
heat sink, on the other hand, uses heat pipe. The problem of
resistance to heat spreading is well tackled by the usage of
heat pipes.
Figure 6: An active extruded heat sink
In present work, the heat sink considered, has a
Copper base and Aluminum plate fins. Studies are conducted
when this heat sink was subjected to flooded and impinging air
flows. The images of the heat sink models considered are
show in figures 7 & 8.
Figure 7: Designed flooded plate fin heat sink with Al fins
and Cu base
N.V.S. SHANKAR* et al. ISSN: 2250–3676
[IJESAT] INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE & ADVANCED TECHNOLOGY Volume-2, Issue-2, 233 – 240
IJESAT | Mar-Apr 2012
Available online @ http://www.ijesat.org 236
Figure 8: Designed plate fin heat sink with impinging flow,
Al fins and Cu base.
With the designed heat sinks, a full case flow simulation was
carried out and the results are presented in the next section.
3. RESULTS AND DISCUSSIONS
The chassis models with the flooded and impinging flow heat
sinks are analyzed using CFD simulation for air flow patterns
and heat dissipation. Four fans are used in simulation, of
which 2 case fans and 1 processor fan were 80 mm axial flow
with 80 cfm and other was a 40 mm chipset fan.
Two orientations of flooded heat sink i.e. parallel flow and
perpendicular flow are initially considered. When the fan of
the flooded heat sink is placed parallel to the inlet case fan, it
is observed that the temperature of the Ram is around 74oC.
The cut plot showing the orientation of the heat sink and the
flow pattern for this case is given in fig 9. Figure 10 and 11
show the flow velocity and density of air in parallel flow
pattern.
Figure 9: Cut plot showing temperature and velocity
distribution for parallel flow flooded cooler
Figure 10: Air density distribution in cabinet for parallel
flow flooded cooler
Figure 11: Air velocity distribution in cabinet for parallel
flow flooded cooler
Figure 12: Cut plot showing temperature and velocity
distribution for perpendicular flow flooded cooler
N.V.S. SHANKAR* et al. ISSN: 2250–3676
[IJESAT] INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE & ADVANCED TECHNOLOGY Volume-2, Issue-2, 233 – 240
IJESAT | Mar-Apr 2012
Available online @ http://www.ijesat.org 237
Figure 13: Air density distribution in cabinet for
perpendicular flow flooded cooler
Figure 14: Air velocity distribution in cabinet for
perpendicular flow flooded cooler
In Figures 12, 13 and 14, the cut plots containing the
perpendicular flow pattern are presented. From the above plots
it can be observed that there is higher air velocity for
perpendicular flow between rams when compared with
parallel flow. This resulted in lower temperatures for RAM. A
comparative graph of predicted temperatures of various
components in both the cases is given in fig 15. Based on the
results it can be observed that the latter is an optimum
orientation. The results of these are taken into consideration
when comparing the performance with those of impinging
flow.
Surface plots showing temperature distribution and heat flux
of the processor heat sink and chipset heat sink for this
orientation are presented in figures 16 to 18.
Figure 15: Comparison of temperatures in parallel and
perpendicular flow orientations
Figure 16: Temperature distribution on processor heat
sink with flooded flow
Figure 17: Heat flux on processor heat sink with flooded
flow
N.V.S. SHANKAR* et al. ISSN: 2250–3676
[IJESAT] INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE & ADVANCED TECHNOLOGY Volume-2, Issue-2, 233 – 240
IJESAT | Mar-Apr 2012
Available online @ http://www.ijesat.org 238
Figure 18: Temperature distribution on Chipset heat sinks
with flooded flow on processor heat sink
Figure 19: Temperature distribution on processor heat
sink with impinging flow
Figure 20: Heat flux on processor heat sink with
impinging flow
Figure 21: Temperature distribution on Chipset heat sink
with impinging flow on processor heat sink
Figure 22: Cut plot showing the air flow pattern in cabinet
with impinging flow on CPU heat sink
Figure 23: Comparison of temperature in impinging flow
and flooded flow
N.V.S. SHANKAR* et al. ISSN: 2250–3676
[IJESAT] INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE & ADVANCED TECHNOLOGY Volume-2, Issue-2, 233 – 240
IJESAT | Mar-Apr 2012
Available online @ http://www.ijesat.org 239
As mentioned earlier, CFD analysis with impinging flow on
multi-material heat sink was also performed. Figures 19 to 22
show the results of the analysis when impinging flow on heat
sink was considered. Based on the surface plots of the
processor heat sinks, it can be observed that there is a slight
lower temperature during flooded flow. A comparative plot of
temperatures of various components is presented in figure 23.
Processor temperature is the main factor of comparison as
processor is the component dissipating maximum amount of
heat in the system. Based on the plot it can be observed that
with flooded flow, the processor and Ram temperatures are
slightly lower, but the chipset temperatures are high. Based on
these observations, it can be concluded that there is
performance gain achieved using a flooded heat sink but at the
cost of increased temperature of other components. In order to
overcome this disadvantage, a better chipset fan or chipset
heat sinks are to be used.
4. CONCLUSION
A study of effect of air flow on the performance of a multi –
material heat sink, with copper base and aluminium plate fins,
using CFD analysis is performed. Two types of air flows are
considered: Flooded flow and impinging flow. Initially flow
simulation is carried for two orientations of the flooded flow
heat sink. It is found that when the heat sink is perpendicular
to the inlet case fan axis, the temperatures of all the other heat
generating components are low. Thus this orientation is
considered for comparison with imping flow configuration
results. Comparing the results of impinging flow and flooded
flow, it is observed that, there is a performance gain with
flooded flow heat sink at the cost of rise in temperature of
other components.
REFERENCES
[1] R. Mohan and Dr. P. Govindarajan, 2010, “Thermal
analysis of CPU with composite pin fin heat sinks”,
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[2] Dong-Kwon Kim, Sung Jin Kim, Jin-Kwon Bae, 2009,
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[3] Jie Wei, 2007, “Thermal management of Fujitsu’s High-
performance servers”, FUJITSU Sci. tech J., Vol 43 - 1,
pp.122-129
[4] Chyi-Tsong Chen, Ching-Kuo Wu, Chyi Hwang, 2008,
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[5] Takeshi hirasawa, Kenya Kawabata and Masaru Oomi,
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[6] Yuichi Kimura, Yoshio Nakamura, Junji Sotaniand
Masafumi Katsuta, 2005, “Steady and Transient Heat
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[7] Sukhvinder Kang, Maurice Holahan, 2003, “The Thermal
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[8] Giovanni Cortella, 2002, “CFD-aided retail cabinet
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[9] Ram Viswanath, Vijay Wakharkar, AbhayWatwe and
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[10] Keller, Kurtis, 1998, "Cast 3D Heatsink Design
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[11] Keller, Kurtis, 1998 "Low Cost, High Performance, High
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[12] Tom Kowalski and Amir Radmehr, 2000, “Thermal
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N.V.S. SHANKAR* et al. ISSN: 2250–3676
[IJESAT] INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE & ADVANCED TECHNOLOGY Volume-2, Issue-2, 233 – 240
IJESAT | Mar-Apr 2012
Available online @ http://www.ijesat.org 240
Datasheet, Volume 1, February 2010, Document #
320834-004
[16] Intel® Core™ i7-900 Desktop Processor Extreme Edition
Series and Intel® Core™ i7-900 Desktop Processor Series
Datasheet, Volume 2, October 2009, Document number:
320835-003
BIOGRAPHIES
N. V. S. Shankar is currently working as
Asst. Professor in Department of Mechanical
Engineering, Swarnandhra College of
Engineering and Technology,
Seetharampuram. He has a total of 8 years
work experience consisting both academic
and industrial.
Rahul Desala is currently pursuing his IV
year B. Tech. (Mechanical) at Swarnandhra
College of Engineering and Technology,
Seetharampuram affiliated to JNTU,
Kakinada.
V. SrinivasBabu is currently pursuing his IV
year B. Tech. (Mechanical) at Swarnandhra
College of Engineering and Technology,
Seetharampuram affiliated to JNTU,
Kakinada.
Dr. P. Vamsi Krishna is working as
Associate Professor in Industrial
Production Engineering Department,
GITAM Univesrsity, Visakhapatnam.
He has 10 years of experience in
teaching and research.
Dr. M. Muralidhar Rao is currently
working as Principal, Swarnandhra
College of Engineering and Technology,
Seetharampuram. He has over 32 years of
experience and has many national and
international publications. He also guided
research projects.